Harness energy to defeat the aliens in this real-time strategy game! Hire soldiers and build towers that will attack aliens and the structures that they crawl from. To build a tower or hire a unit, you'll need energy, which is produced by the towers and sometimes released by an enemy in the form of a lightning bolt. You can only build a tower near your base or in the range of another tower. You also control a hero and have special abilities that can be used when fully charged. Upgrade your towers, soldiers, abilities, and hero between missions.